Novel application of low carbon limestone calcined clay cement (LC3) in expansive soil stabilization: An eco-efficient approach

This article presents the novel application of new ternary low carbon limestone calcined clay cement (LC3) to deal with construction problems associated with problematic expansive soils. Such soils exhibit high volumetric change behavior and cause extreme distress or failure to the overlying engineering structures. Various calcium-based admixtures such as lime and ordinary Portland cement (OPC) have been extensively used to mitigate its adverse effects, but have a huge environmental impact in terms of high carbon footprints. In this regard, recently developed low carbon LC3 has been applied in concrete technology for various purposes, however, its efficacy for expansive soil stabilization is still unknown. Therefore, this study for the first time investigates a wide spectrum of macro-micro properties of LC3-treated soil and reveals its underlying stabilization mechanism. LC3 addition exhibits complete mitigation of swelling behavior, reduced saturated hydraulic conductivity along with significant improvement in compressive strength considering the long-term curing period. The stabilization mechanism reveals that corresponding amelioration in engineering properties falls under three phases; 1) cation exchange; 2) flocculation or agglomeration, and 3) hydration products such as calcium aluminosilicate hydrate (CASH), coupled with AFt (ettringite) phases which act as a filler material by creating a high pH environment. Estimation shows that LC3 usage in place of OPC for expansive subgrade of the 1-km two-lane road can save consumption of approximately 350 GJ and 12594 kWh of thermal and electrical energies, respectively, and CO2 emission of around 27420 kg of C. Overall, the LC3 application in problematic expansive soil stabilization not only adds a new dimension but also provides a sustainable and environmentally friendly alternative to reduce the carbon footprints of traditional techniques.